Process for oxidizing olefins to aldehydes and ketones



W. RIEMENSCHNEIDER ETAL PROCESS FOR OXIDIZING OLEFINS TO ALDEHYDES AND KETONES Filed Oct. 28, 1958 muni@ lkl x25.. om .55. ...ou

III-'l ATTO United States Patent C 3,076,032 PROCESS FOR OXiIiZlNG OLEFiN 'IO ALBEHYDES A'ND KETONES Wilheirn Riemenschneider and Kurt Diaier, Frankfurt am Main, Germany, assignors to Farhwerire Hoechst Aktiengeselischatt voi-mais Meister Lucius z Brning, Frankfurt am Mm'n, Germany, a corporation of Ger- Filed Oct. 2S, 1958, Ser. No. 770,007 Claims priority, appiication Germany Oct. 31, 1957 6 Claims. (Cl. 26o-597) The present invention relates to a process for oxidizing :olens to 'aldehydea ketones and acids.

It has already been proposed to .oxidize ethylene catalytically by means of an argentiferous catalyst to ethylene oxide, or by means of 'an oxidation catalyst other than a silver-containing catalyst at a raised temperature .to obtain mixtures Vof formaldehyde, acetaldehyde, formic acid, acetic acid and other products. These processes, however, do not produce acet'aldehyde or acetic -acid in a yield interesting from an economical point of View. Our experiments have revealed that the oxidation carried out under such conditions in the presence of a noble metal catalyst likewise involves small yields of acetaldehy-de, and the relative proportion of formaldehyde obtained generally preponderates.

lt is also known that compounds of palladium, platinum, silver or copper form complex compounds with ethylene. Furthermore, the formation 'of acetaldehyde was observed in decomposing a potassium-platinum-complex compound. Other unsaturated compounds may favo-r the complex formation. In this case stoichiometric reactions are concerned yielding the noble metal as such.

it has also been described to reduce palladous chloride by means of ethylene in the presence of water to palladium metal. ln this reduction the formation of acetalde-` hyde was observed.

Still further, it has been described that palladous chloride dissolved in Water can be reduced rapidly and completely to palladium by means of propylene, even if propylene, even if propylene is admixed with nitrogen or air. It has also been described to reduce palladous chloride by means of isobutylene under the same conditions. It is described that carbon dioxide is not evolved either in this latter reduction or in those reductions which are carried out in the presence of ethylene or propylene as a reducing agent.

'ln application Ser. No. 747,116 filed July 8, 1958, a process is described according to which lcarbonyl compounds can be obtained from the corresponding oleiins in a goo-d yield and, if desired, in `a continuous manner by contacting said oleiins With an oxidizing agent, a liquid catalyst having an acid to neutral reaction and comprising Water, a compound of the noble metals be longing to group VIH of the periodic table and a redox system.

It is furthermore described in application Ser. No. 750,150 filed l'uly 22, 1958, to contact the olefin and the oxidizing agent separately with the liquid catalyst. According to said application the reaction may be performed by contacting the liquid catalyst with the olefin and the oxidizing agent in several reaction vessels. Instead of pure olelin a mixture of oxygen and oleiin may be used in which the oxygen content is outside the range of explosivity, i.e. for example between 1 and 10%, calculated upon the amount of oleiin used.

In application Ser. No. 747,115 tiled July 8, 1958, a process is described according to which carbonyl compounds can be obtained from the corresponding oleins in a good yield and, if desired, in a continuous manner by contacting said oleiins with gaseous oxygen, water which is present in the vaporous form, and a solid catalyst erably air.

3,@76032? Patented dan. 29, 1953 ice which contains a compound of a noble metal belonging to group VIII of the periodic system as catalytic substance and a redox system.

In application Serial No. 760,539 filed September 12, 1958, now U.S. Patent 3,057,915 granted October 9', 1962, it is described that the yield of acids which correspond to the aldehydes can be considerably increased without the aldehyde yield being reduced when an olen is contacted with gaseous .oxygen in the presence of Water vapor Vand a solid -acid to neutral catalyst containing as carrier a compound of a noble metal of group VIII of the periodic system and a redox system containing one or more compounds of yone or more metals having an latomic number in the range from 25 to 27, i.e. iron, manganese, and/or cobalt.

In application Ser. No. 763,691 tiled September 26, 1958 and now abandoned it has been disclosed that the olens may even be diluted by carbon monoxide and/or hydrogen and that the course of the reaction is not atfected by the presence of these gases.

AMoreover it has been disclosed in application Ser. No. 765,272 tiled October 6, 1958, to obtain acetaldehyde and/or acetic acid by oxidation of ethylene by means of an oxidizing agent, preferably molecular oxygen, if desired in admixture with inert gases at an elevated temperature and under an elevated pressure in the presence of water and an inorganic redox system, in which the metal component is at least monovalent in its reduced stage of valence. For example redox systems may be used which contain compounds of Cu, Fe, Co, Ni, Mn, Hg, Ce, Ti, U, Bi, "Il, Sn, Pb, Cr, Mo, V, Sb, or mixtures of such compounds.

Finally it has been described in application Ser. No. 768,624 filed October l0, 1958 that when using coppercontaining catalysts in the reaction described in the aforementioned applications the conversion is dependent on the molar ratio of copper to halogen and that it is therefore very favorable to keep the molar ratio of copper to halogen and more especially of copper to chlorine Within the limits of 1:1 and 1:2, preferably within 1:1.4 and 1:1.8; in this case it is inmaterial whether a solid, liquid or more especially an aqueous catalyst is used. When using a liquid catalyst it is therefore advisableA to supply halogen ions during the reaction in very accurate dosages.

The yabove ratio of copper to halogen should be understood to include the amount of halogen added in the form of iron halide or another halide of cations which do not form neutral reacting salts with hydrohalic acids. The amount of halogen which is present in the form of Ia neutral salt, for example sodium chloride or potassium chloride, or is capable of being bound to form a neutral salt, need not be considered. For example, if the catalyst contains 3 gram equivalents of alkali metal salts or alkaline earth metal salts of acids other than hydrohalic acids, 5 gram equivalents (mols) of chlorine ions ladded in the form of iron chloride, and 1 mol of copper ions added in the form of copper acetate, the copper to chlorine ratio is 1:2 according to the definition given above.

In the aforesaid applications the term carbonyl compounds is used in its broad sense, i.e. it covers'not only aldehydes and ketones but also carboxylic acids such as acetic acid.

lt is supposed that in the reaction described in the aforementioned applications the oxidation of the redox system added, i.e. for example the oxidation of intermediately formed cuprous chloride to cupric chloride, is the velocity determining step for the entire reaction. Since it is advantageous to accelerate a slow reaction in order to arrive at a high conversion, care must be taken that the redox system undergoes rapid oxidation by the oxidizing medium, such as oxygen or gases containing oxygen, pret- Oxidation may be accelerated by a tine distribution of the oxidizing gases or by operating under a raised partial pressure of oxygen, or by addition of an inorganic oxidation promoter.

In carrying out the reaction with oxygen or gases containing molecular oxygen and with a solid or a liquid catalyst We have now unexpectedly found that the reaction velocity and olefin conversion are increased or, if the rate of conversion remains the same, that the throughput is considerably increased by operating in the presence of a redox system, especially of inorganic nature, and a quinone which, if desired, may have been rendered watersoluble by substitution with sulfonic acid and/or carboxylic groups. The aforesaid quinones or their substitution products or the water-soluble salts thereof facilitate the oxygen transition from the gaseous to the liquid phase.

As quinones vthere may be used, for example, orthoand/ or para-quinones, 'such as benzoquinones, naphthoquinones, anthraquinones, phenanthrenequinones, or alkyl substitution products of such quinones, or the substitution products thereof, which have been referred to above. By adding, for example the potassium salt of 1.2-naphthoquinone-l-sulfonic acid to a dilute copper chloride catalyst activated with palladium chloride, the conversion is more than doubled as compared with a catalyst free from such addition. K

As quinones there may, for example, also be used ben- 4zoquinone, tetrachlorobenzoquinone, 1,2-naphthoquinone- 4-sulfonic acid, l,2-naphthoquinone-4,7disulfonic acid, l,4-naphthoquinone-Z-carboxylic acid, -Z-Sulfonic acid, S-sulfonic acid, -2-,6-disulfonic acid, '-2,3-dicarboxylic acid, anthraquinone-l-carboxylic acid, -2-carboxylic acid, -l-sulfonic acid, -2-sult`onic acid, 1,5-disulfonic acid, -l,8 disulfonic acid, -2,6disulfonic acid, 2,7disulfonic acid, anthraquinone l'- carboxylic 2-sulfonic acid, 2-ethylanthraquinone-sulfonic acid, phenanthrenequinone- 1 sulfonic acid or soluble salts thereof, in which the cation is e.g. an alkali salt, such as ammonium, sodium or potassium. Soluble alkaline earth metalsalts may likewise be used. Furthermore mixtures of the aforesaid compounds may be applied.

The quinones or theirY sulfonic or carboxylic acids or the water-soluble salts of quinone sulfonic acids or quinone carboxylic acids are preferably used in a proportion of up to by Weight, calculated upon the amount of catalyst, and preferably in a proportion of between 0.1 and 3% by weight. If the oxidation is carried out in two stages as set forth in application Ser. No. 750,150, it is possible, prior to or during the oxidation of the catalyst, to substitute the corresponding hydroquinones for the quinones or quinone compounds mentioned above, and

to oxidize these hydroquinones to q-uinones.

The use of the aforesaid quinones or their derivatives enables the amount of catalytically active substance in the catalyst, and also the prime cost of the catalyst and the formation of by-products to be reduced.

The present invention may be carried out with the catalysts and under the conditions broadly described in the above mentioned applications, for preparing carbonyl compounds from the corresponding oletins, i.e. olefins having the same number of carbon atoms as the carbonyl compounds. These catalysts contain one or more redox systems and preferably a compound of a noble metal of group VIII of the periodic table, particularly palladium.

As redox systems which may be present there are, for example, mentioned those that contain compounds of metals which under the reaction conditions employed may appear in various oxidation stages, for example compounds of copper, mercury, cerium, thallium, tin, lead, titanium, vanadium, antimcny, chromium, molybdenum, uranium, manganese, iron, cobalt, nickel or osmium, the latter preferably in admixture with compounds of other of the aforesaid metals, and also inorganic redox systems other than specified above, such as subite/sulfate, arsenite/arsenate or iodide/iodine systems and/or organic redox systems, for example azobenzene/hydrazobenzene, or quinones or hydroquinones of the benzene, anthraceneor phenanthrene series.

As compounds of the noble metals of groupI VIII of the periodic table there may be used in the process according to the present invention, for example compounds of palladium, iridium, ruthenium, rhodium or platinum, i.e. of metals, the stable valence of which is at most 4. Compounds of this series of metals are believed to be capable of forming addition compounds or complex compounds with ethylene. The reaction may likewise be carried out in the presence of a noble metal.

As oxidizing agent there may be used, for example, oxygen, if desired in admixture with an inert gas. The oxygen may be employed, e.g. in the form of air, which is the cheapest oxidizing agent, or in the form of air enriched with oxygen. The use of airis, however, confined to certain limits, if the unreacted gases are circulated, inasmuch as nitrogen concentrates as ballast material. Instead of ethylene there may also be used a gas mixture containing ethylene and, for example, saturated hydrocarbons.

The reaction Imay be supported or carried out by addition of an active oxidizer, such as ozone, peroxidic compounds, especially hydrogen peroxide or sodium peroxide, potassium peroxide, potassium persulfate, ammonium persult'ate, alkali percarbonate, alkali perborate, peracetic acid, diacetyl peroxide, benzoyl peroxide, toluyl peroxide, oxygen compounds of nitrogen, such as nitrogen dioxide and nitrogen pentoxide or mixtures of nitrogen oxidesv containing the same, nitryl halides such as nitryl chloride, free halogen such as chlorine, bromine, or bromotrichloride, halogen-oxygen compounds such as chlorine dioxide, hyprochlorous acid, chloric acid, perchloric acid, bromic acid, iodic acid, periodic acid, or compounds of the higher valence stages of metals, such as manganese, cerium, chromium, selenium, lead, vanadium, silver, molybdenum, cobalt, or osmium, for instance potassium permanganate, sodium bichromate, lead tetraacetate, vanadium pentoxide, silver diiiuoride, selenium dioxide, cerium-(IV) sulfate, osmium tetroxide. The addition of an active oxidizer facilitates the re-formation of the higher oxidation stage of the active catalyst component which is necessary for carrying out the reaction. These oxidizing agents may also be produced during the reaction. If desired, an oxidizing catalyst may be added. It is often advantageous to add, prior to or during the reaction, a compound yielding anions under the reaction conditions applied, for example an inorganic acid, preferably a mineral acid, such as sulfuric acid, nitric acid or a volatile acid, such as hydrochloric acid or hydrobromic acid, or a salt such as ammonium chloride, ammonium bromide, zinc chloride, aluminum chloride, iron chloride, chromic chloride, titanium tetrachloride, sodium hydrosulfate, a halogen or a halogen-oxygen compound, for example those mentioned above, or thionyl or sulfuryl chloride, or also an organic substance, preferably a saturated aliphatic halogen compound of low molecular Weight such as ethyl chloride, propyl chloride, butyl chloride, acetyl chloride, benzoyl chloride, propionyl chloride, phosgene. Such addition enables a possible decrease of anions to be counteracted and the lifetime of the catalyst to be prolonged.

In case the reaction is carried out in the presence of solid catalysts and that non-volatile compounds yielding anions are used as listed above, these substances are, of course, added to the catalyst before the reaction, while the volatile compounds can be added as well before as during the reaction.

The process of the present invention is carried out at relatively low temperatures and may be carried out as well in the presence of a solid catalyst as in solution. If solid catalysts are used suitable Contact supports (carriers) are, for example, silicagel, kieselguhr, pumice, silicates, TiO2, A1303, active carbon, acid ion exchangers,

such as Amberlite IRC 50, Dowex types 60, permutites, phenol-aldehyde-resins which are substituted by sulfonic acid groups, polystyrene-resins which are substituted by sulfonic acid groups and cross-linked by divinyl benzene etc., or mixtures of such carriers.

lf liquid catalysts are applied a pure aqueous solution is preferably used, but the reaction may likewise be carried out in aqueous solutions in which the water is diluted with a hydrophilic solvent such as acetic acid, acetone, methylethylketone or other ketones, ethylene glycol, propylene glycol, glycerol, dioxane or mixtures thereof.

lf the present process is carried out in the presence of noble metals of group VIH of the periodic system and of redox systems, it can be carried out with special advantage at temperatures within the range between S and 160 C., preferably 50 and 100 C.; if it is carried out in the liquid phase, it is necessary to operate under a raised pressure provided that the temperature used is above 100 C. If desired, the process may also be carried out at temperatures outside the ranges indicated above, for example at 170 C. to 180 C., or for example at 40 C., or within a range of, for example, 80 C. to 120 C. Furthermore atmospheric pressure, a raised pressure or reduced pressure may be applied, that is, a pressure of up to 100, preferably of up to 50 atmospheres gauge. The process may be carried out under pressure regardless of whether the temperatures used are above or below 100 C. it is furthermore of importance to carry out the process in an acid to neutral medium. The preferred pH- values are within the range between 0.8 and 3; higher pH-values between, for example, 0.8 and 5 or 2 and 6, or lower pH-values, for example, 0.5 may also be used, although such pH-values generally do not involve a special advantage.

lf the present process is carried out in the absence of noble metals and in the presence of inorganic redox systems, as disclosed in application Ser. No. 765,272 mentioned above, generally a temperature between 50 and 250 C., more suitably between 100 and 250 and preferably between 130 and 200 C. and pressures above atmospheric pressure and below 400 atmospheres (gauge pressure). more suitably between and 200 atmospheres (gauge pressure) and preferably between 80 and 120 atmospheres (gauge pressure) are applied. Of course the reaction may be carried out at lower or higher temperatures, for example above room temperature, or under a higher pressure, for example at 450 atm. In this embodiment of the present invention operating at pH-values between land 5 is most preerred, though operating at higher or lower pH-values, for example at pH 0 is likewise possible. lr solid catalysts are used the solution with which the solid catalyst is impregnated may be adjusted so as to have a pH within the limits indicated above.

Liculties which may appear in working in the liquid phase can be overcome by modifying the ratio of olen to oxygen. Such difficulties may reside in the precipitation of cuprous chloride or other compounds formed which cause cloggings and undesired disturbances in operation. In view o the fact that these precipitated salts are no longer available for the reaction, the yield decreases more or less rapidly. The moment at which the olen to oxygen ratio must be modified, can be readily determined by continuously measuring the pH.

if the pH decreases, it is easily possible to readjust the optimum pli-range by adding either more oxygen or less olelin, lor by combining these two steps. If the pH increases, the optimum ,pH-range can be readjusted inversely. This method of controlling the reaction may also be combined with the above described addition of compounds yielding anions, for example hydrohalic acid or organic compounds splitting olf hydrohalic acid under the reaction conditions, or acid salts. It is especially advantageous to adjust 'the reaction medium to `a certain pH at the onset of the reaction, for example by means of hydrochloric acid, and to regulate the `olelin-'oxygen ratio during the reaction. The pH may of course also be modiiied during the reaction by addition of an acid.

The pH is measured by using a device of known type. The pH may be measured continuously with electrodes arranged in the reactor, or discontinuously by measuring the pH of samples withdrawn in certain intervals of time. In a special technical variant of this meth-od the pH- measuring device has an automatic connection to the dosing device for the supply of ethylene and oxygen. In this case the pH is once adjusted to the optimum value and the reaction can then be controlled automatically.

Sometimes the presence of a salt, such as sodium chloride or potassium chloride may prove advantageous. For example, these saltslike hydrochloric acid itself or other alkali metal or alkaline earth metal halides such as LiCl, CaCl2, MgCl2 or other salts such las FeCl3, FeClZ, ZnClZ or CuCl2-improve the solubility of CuCl, which may be formed in the course of the reaction and which is only very sparingly soluble in water (0.11% at C.). In solid catalysts the reactivity of CuCl may for instance be improved by the presence of such salts.

The reaction may be supported by increasing the ethylene and/or oxygen concentration in the reaction space. This can be achieved, for example, by increasing the pressure and/-or-especially when the reaction is carried out in the liquid phaseby the presence of a solvent. The ethylene concentration in the reaction solution may be considerably increased, for example, by using higher concentrations of metal salts binding ethylene, for instance copper, inon, mercuryor iridium compounds, especially halides, yor the sulfates, the latter especially when mercury is concerned, or by using organic solvents which are preferably miscible with water, for example acetic acid, methylethylketone or other ketones, monoor polyhydnic alcohols, acyclic ethers or dimethyl formamide. The gases may be circulated; if desired, for example a gas containing a few percent of unreacted oxygen.

Due to the presence of oxidizing agents acetic acid may be formed in a small amount in addition to acetaldehyde. If desired, the oxidation of ace'taldehyde to acetic -acid which is known in the art, may be combined with the reaction described above in order to omit partially or totally the aldehyde stage, or acetaldehyde may be oxidized in a second stage in known manner to acetic acid, eg. in the presence of manganese compounds.

Under the conditions specified above under which ethylene yields acetaldehyde, propylene yields preponderantly acetone and pnopionaldehyde. a and -butylene yield preponderantly methylethyl ketone, the ot-butylene yielding also butyraldehyde, and isobutyraldehyde can be obtained from isobutylene. in the case where higher olefins are concerned, such as pentene and its homologs, cyclohexene or styrene, the reaction proceeds substantially in a manner analogous to that described and it can be carried out under the same conditions as set forth above. Due to the relatively mild reaction conditions there are almost exclusively obtained those oxidation products which had to be expected in view of their structure, without noteworthy isomerizations or molecule decompositions occurring.

Mixtures of oleiins or gases containing oleiins or other unsaturated compounds may be reacted in the same manner, provided they are capable of reacting under the reaction conditions, for example diolens. The reaction of oleiins containing 2 to 3 carbon atoms is however preferred. Under circumstances, the reaction conditions must be adapted to the compounds used and to their physical properties. The higher boiling points of the reaction products may also require a corresponding modication of the reaction conditions. Diacetyl may be obtained, for example from butadiene.

As stated above the reactants may be diluted by gases inert towards the reaction, for example by nitrogen, carbon dioxide, methane, ethane, propane, butane, isobutane, and other saturated aliphatic compounds and furthermore by other compounds such as cyclohexane, benzene or toluene.

The olefins may however not only be diluted by one or more of the aforementioned gases, but likewise with carbon monoxide and/ or hydrogen, if desired in addition to the aforementioned gases. If such gas mixture contains CO, oxygen should be present at least in an amount as is necessary to convert the olefin to aldehyde and carbon monoxide to carbon dioxide.

It is believed that olelin-noble-metal complex compounds are formed as intermediary products which then react with water to yield carbonyl compounds. It is however known from the literature that carbon monoxide expels from these coordination compounds all oleiins, including ethylene. For these reasons a mixture of olens with carbon monoxide was expected to bring about none or only a very small conversion of the olefin to carbonyl compounds. It is therefore surprising that a mixture of carbon monoxide and olefin, if desired in admixture with one or more other gases inert towards the reaction such as those mentioned above, practically yields the same amounts of carbonyl compounds as if no carbon monoxide were present. In this reaction the carbon monoxide is partially converted to carbon dioxide.

It is also known from the pertinent literature that hydrogen reacts in a manner very similar to that of carbon monoxide, and it is therefore just as well surprising that the olefin oxidation takes an absolutely smooth course in the presence of hydrogen. The maior amount of hydrogen remains unaltered, whereas a -small portion thereof reacts with formation of water and another small portion with hydrogenationof the oleiins.

The carbonyl compounds can be obtained in the same manner without areduction in conversion occurring by using a mixture of carbon monoxide and hydrogen with an ol-eiin or a gas containing an olefin; in this case, it is sometimes favorable for the conversion to work with the applicationy of pressure.

The fact that neither hydrogen nor carbon monoxide affect the process of the invention is of special advantage since accordingly industrial gases, for example reiined gases or gases obtained in cracking processes may be used as starting materials. All expensive gas separations can therefore be dispensed with, although a prepuriiication oer concentration of the olefin may prove advantageous, so that a considerably cheaper crude material can be used. Carbon monoxide and/or hydrogen may appear in the gas mixture, for example in double the amount of the olefin,

and yet the oleiin oxidation is not substantially impaired.

This statement is however, not intended to indicate a limit. If these gases are present, it is especially suitable to use the multiple stage process described in application Ser. No. 750,150, in which the olefin, if desired in admixture with a small amount of oxygen, is contacted with the catalyst in one stage, While the oxidizing agent is contacted with the catalyst in a second stage or apparatus. This modification of the present process is broadly described below; as a result of these measures it is possible to practically avoid a mixing of the gases used with oxygen, so that the forme-r can be used for further purposes after having left the reactor.

For stoichiometric reasons the molar ratio of olefin to oxygen must be 2:1 in the complete -oxidation of oletins to the corresponding aldehydes or ketones. To prevent explosions, it is however preferred to use an oxygen deliciency, for example in the range of 2.5 :l to 4: 1. Still further it is preferred to Work outside the range of explosivity, for example with a content of oxygen of 820% or 8-l4% under pressure, and to circulate unreacted gas which consists substantially of nonconverted oleiin, if desired in admixture with other inert gases, such as nitrogen and/or with hydrogen and/or carbon monoxide, and which may furthermore contain some oxygen. To this gas oxygen and the olefin such as ethylene are added as they are consumed.

The present process may be carried out for example by contacting the olefin and oxygen or air simultaneously with the catalytic substances. However, it is often very advantageous especially if liquid catalysts are used, to contact the olefin and the oxidizing agent separately with the liquid catalyst used. This mode of operating has the advantage that the compositions of the gas mixture need not be controlled carefully and that even in recirculating the olefin, such as ethylene, air may be used as oxidizing medium Without disadvantages being involved. This variant may be performed by contacting olen and oxidizing agent in periodic alternation with the circulating catalyst liquid in a vessel; in a continuous operation there may beused to this end a reciprocally reversible double apparatus, or olelin andV oxidizing agent are contacted with the circulating catalyst liquid in several reaction vessels. In this variant, pure olefin or an clelia-containing gas may still contain oxygen, the oxygen content being outside the range of explosivity, i.e. for example, between 1% and 10%, preferably between 3% and 10% of oxygen, calculated upon the amount of olefin used. For example, the explosive limit of an ethylene-oxygen gas mixture is at atmospheric pressure at 20.1% of oxygen. In this modilied variant the reaction is preferably'carried out in such a manner that the oxygen is almost or completely consumed in theV reaction vessel and the catalyst is then regenerated in the regeneration vessel, where the Contact medium -is contacted with the oxidizing medium, for example oxygen -or air, in an amount sufficient to bring about regeneration. Regeneration is brought about under known conditions, for example at 50-150" C., and may be carried out under pressures and at temperatures being different from those of the first stage in which the catalyst is contacted with the olefin.

Depending on the conditions applied in this case the olefin dissolved in the catalyst medium is also oxidized and the dissolved reaction product is :removed by stripping. In order to produce a good stripping effect, regeneration may also be brought about using mixtures of oxygen or air with steam.

Contacting olefin and oxidizing agent separately with the catalyst medium involves the advantage that the process can always be carried out under atmospheric pressure and, more especially under superatmospheric pressure, with gas mixtures which are outside the inliammability limit and absolutely harmless.

As compared with the variant of contacting the olefin per se and the oxidizing agent per se with the catalyst medium, the use of a mixture of oleiin with a small amount of oxidizing agent in one stage and of additional oxidizing agent in the second stage offers the further advantage that an occasional separation of undesired solid products is avoided at the place Where an .olefin-oxygen mixture enters into the reactor, which contains oxygen in an amount smaller than corresponds to the stoichiometric composition as regards the conversion to the carbonyl compounds, and the composition of which gas mixture is outside the infiammability limit. A separation of solid substances would cause reduction of the catalytically active substance in the catalyst liquid and accordingly a reduction of the catalyst activity; on the other hand, such separation would involve cloggings in conduits, cocks or nozzles. Such separation of solid substances does not appear if a minor amount of oxygen or air is admixed with the olefin and such mixture is contacted in the lirst stage with the catalyst solution, and if the catalyst solution is regenerated in a second stage by addition of a further amount of oxidizing agent. If the olefin and the oxidizing agent, or an olefin containing a small amount of oxygen and the oxidizing medium, for example oxygen, are contacted separately in the manner described above with the catalyst, it may be advantageous to free the Iolefin-treated catalyst solution before it is being contacted in a second phase with the oxidizing gases, from residual unreacted oleiin and residual reaction product, for example by stronger heating or stripping with an inert gas, such as nitrogen or steam. By connecting the head of the reaction tower of one phase with the lower liquid inlet of the regeneration tower and vice versa, it is possible to produce a closed liquid cycle, so that pumps can be dispensed with. The ascending gas currents circulate the liquid vigorously; this circulation can be measured by flow meters or another suitable device.

If it is feared that the mixture comprising residual oxygen or residual air and aldchyde, for example acetaldehyde, could rise 4slightly above the lower explosive limit, the head yof the regeneration tower may readily be provided with a safety device of known type to prevent explosion, such as bursting disks, a darne trap such as pots fille-d with steel grains or the like. The danger of explosion is however extremely low in view of the acetaldehyde-oxygen-mixture being saturated with water vapor and in view of the relatively low content of oxygen, which is smaller than the oxygen content of the air.

The present process may, es. be carried out in an apparatus shown in the appended drawing. A current of oleiins or of an olelin-containing gas is introduced through a compressor i into reactor 2 or 2a in direct or countercurrent to the catalyst liquid, and the gas is finely distributed in the catalyst solution by means of a suitable device, for ex .ple a frit, a mixing nozzle, an oscillatory sieve, a vibrator, a rapid agitator or the like.

The oleiin is converted in this solution to a carbonylcontaining reaction product leaving the reactor together with unreacted o-len, if desired via a cyclone 3. The reaction product is separated in a separating device 4 from unchanged oien or a mixture of unchanged olefin and diluting gas, which may then be recirculated together with a fresh amount of olefin into the reactor via compressor i, or may Icompletely or partially be used for other purposes, especially if the remaining gas mixture contains no substantial amounts of olen. The reaction liquid is then conducted to a stripper 5, where it is treated with steam t-o be directly or indirectly freed from olefin and residues of reaction product. The gases lobtained by stripping are conducted, if desired, to separating device 4. The stripped reaction solution is then introduced into `regenerate-r I by means of a pump 6 or a static incline. The stripping stage may however be omitted, and the reaction solution may accordingly directly be introduced into regenerator The solution is intimately contacted in regenerator 7 with oxygen or gases containing oxygen. The regenerator may be designed so that the contact liquid iiows in a counter-current to the oxygen-containing gases, whici rleave the regenerator through cyclone 8, and may be returned into the cycle by means of a compressor. The contact liquid is then communicated in the regenerated state to reactor 2 or 2a by means of pump 9. All partial operations may be carried out individually or together at a raised pressure, at a reduced pressure, or at atmospheric pressure.

The aforesaid two-stage embodiments have the mutual advantage, that explosive gas mixtures are not liable to occur `.ven when operating under a raised pressure, and that each gas current can be circulated separately and replenished by fresh gas to the necessary extent. It is also possible to use as oxidizing agent in view of the fact that a concentration of nitrogen has here no detrimental effect.

if it is intended to prepare large amounts of acid which correspond to the aldehydes simultaneously with other carbonyl compounds, such as aldehydes, an olefin, if desired in admixture with an inert gas and/ or with hydrogen and/ or carbon monoxide is contacted with gaseous oxygen if desired in the form of air in the presence of water vapor at a solid acid to neutral catalyst comprising a carrier, a compound of a noble metal of group VIH of the periodic system and a redox system'containing one or more lcompounds of one or more metals having an atomic number in the range from 25 to 27, i.e. iron, manganese and/or cobalt. In this case, the compounds of iron, manganese or cobalt are added to the catalyst in the usual manner. t is possible, for example, to impregnato the catalyst with the soluble salts of these elements and to convert these salts by heating, preferably with air, to the iirmly adhering oxides. There may also be used a mixture comprising the aforesaid compounds.

The acid formed can be readily separated from the corresponding aldehyde. lt is preferred to concentrate the acid, which has always a boiling point higher than the aldehyde, in a first separator, and to concentrate the aldehyde which has a boiling point lower than the acid, in a second separator. Both separators are connected in series. The simultaneous production of carboxylic acids and aldelrydes at solid catalysts containing an iron, manganeseand/or cobalt salt, is preferably carried out in the presence of further redox systems, such as copper compounds.

In a frequently useful technical variant of the process of this invention, the desired reaction product, for example acetaldehyde and, if desired, acetic acid, is separated from the reaction gas, the residual gas which may still contain inert gas and/or hydrogen and/ or carbon monoxide and may be free from oxygen, but may likewise contain oxygen, is reintroduced into the reactor, suitably into its lower part and an amount of olefin and, if desired, oxygen corresponding to that consumed during the reaction is introduced into the reactor through one or more inlets which may be arranged one above the other or one behind the other, or the olefin and/or the oxygen are added to the recircuiated gas. For example, the ethylene or ethylene-containing gas is admixed with the residual gas in an amount corresponding to that consumed. The resulting gas mixture which may be free from oxygen or in which the ratio of olen and oxygen is, for example, 95 to 99 percent or to 95 percent of olein (for example ethylene) to 5 to l percent or l() to 5 percent, resp. or" oxygen, is then introduced into the reactor. For the sake of security the oxidizing agent, i.e. preferably oxygen, if desired in admixture with inert gases, such as present in air, is preferably introduced through separate inlets especially when about stoichiometric amounts of the reactants are applied and no diluting gas is present.

The oxidizing agent preferably is introduced below the inlet for the residual gas or, if a circulating catalyst is used, into the circulation conduit of the catalyst. The amount o oxygen introduced may be so modiiied that even in the catalyst solution the explosivity limit is nowhere surpassed. Such modiiication is generally not necessary; itis rather' suiiicient to add the oxygen to the residual gas which escapes from the contact soiution, in an amount to keep the composition of this residual gas outside the xplosive limits.

"in order to obtain especially high spacetime-yields, it is also possible to introduce either oletin or oxidizing agent, preferably oxygen, or olen and oxygen into the reaction vessel, for example a reaction tower, at various places arranged one above the other or one behind the other. Preferably the inlets for each reactant are locally separated frorn the other inlets for the same reactant. it is likewise possible that the amount of yoxygen introduced is measured so as to be at all places of the reaction vessel below the lower limits of the explosive range.

lf the reaction is carried out in the presence of liquid catalysts it may be advantageous to add a dispersant, for example an alkylphenyl sulonate `or a product obtained by the reaction of ethylene oxide, propylene oxide, or butylene oxide with phenols or aliphatic alcohols, and/ or a protective colloid, such as proteins or gum arabic to the liquid catalyst. Finely dispersed solid substances may also be added, if desired. The activity of these substances resides in the fact that free noble metal which has intermediately formed and is reconverted into active cornpounds by the reactants used in the instant process, cannot aggregate to form large particles. The catalyst is therefore especially finely distributed, and the degree of distribution is stable. As solid pulverulent substances there may be used, for example, charcoal powder or kieselguhr. yIt is also possible to use a combination comprising dispersant, protective colloid` and iinely distributed solid substances.

in many cases the reaction proceeds likewise smoothly if the catalysts used contain only a small amount of compounds of the noble metals belonging to group Vlll of the periodic table. in most cases it is sucient to use a catalyst in which the ratio of the sum of the redox metals, especially the sum of copper and iron to the noble metal, especially palladium, is at least :1, preferably 25-500:1. lt is, however, preferred to use a catalyst containing copper salts, in which the-ratio of copper to pallidium is above 10:1, for example above 15:1 and preferably 50:1 to 500:1,nor even above these ranges. This method of operating is more economic in view of the fact that the expensive palladium salt need only be used in a minor amount; it can be used for converting ethylene and oleiins other than ethylene, and may be combined as desired with variants hereinbefore or hereinafter described. This embodiment may also be carried out under elevated pressure.

The reaction of the present invention is favorably in luenced by irradiation with rays rich in energy, preferably ultraviolet light, especially in the case where oxygen is used as oxidizing medium. Such radiation which may also comprise X-rays activates especially the oxygen, increases its oxidizing activity, and promotes both the rcaction with the oleiin and a possible oxidative destruction yof by-products, for example oxalic acid. These measures increase the conversion, reduce the formation of by-products and considerably prolong the lifetime of the catalyst, the activity of which may subside after a prolonged time.

In practice it is advantageous to use a mercury quartz lamp as source of radiation arranged in the catalyst so that the light energy is fairly substantially utilized. lf the reaction is carried out with an apparatus into which oxygen or an oxygen-containing gas is introduced separately from the olenn or olefin-containing gas or even a mixture of the said reactants, it is preferred to arrange the source of radiation in the vicinity of the oxygen inlet, so that that part which is rich in oxygen is especially well irradiated. The oxygen is thereby activated as long as it has a high partial pressure. In the present process, especially in an apparatus, in which the catalyst is circulated, it is advantageous to arrange the source of radiation at the lower end of the contact line or, if the reaction is carried out in several stages, at the lower end of the regeneration vessel, immediately above the oxygen inlet. Activation may also be brought about by adding a compound of a radioactive element to the catalyst solution- It is known that at a constant volume of the reaction liquid and in the case where the reaction does not run completely in one direction, the rate of conversion is the better, the higher and narrower the design of the reactor. lt is also evident that such reaction proceeds the better, the iiner the gaseous components are distributed in the liquid. he catalyst solutions suitable for use in the process of this invention have sometimes the property of foaming after some time. On the one hand this favors the reaction in view of the fact that the gases are finely distributed in the catalyst liquid; sometimes foam-forming agents are intentionally added to the liquid. On the other hand, foaming means that the reaction space available is only insufficiently used, since only part of the contact solution is in the reactor.

If copper and halogen are present it has proved to be advisable to keep the molar ratio of copper to halogen and more especially of copper to chlorine within the limits of 1:1 and 1:2, preferably within the limits of 121.4 and 111.8 as it is described in application Ser. No. 768,624.

If halogen is present in a proportion smaller than corresponds to the ratio of 1:1, the conversion is reduced. In this case the optimum ratio can be readily re-adjusted, for example by addition of hydrogen halide, for example hydrohalic acid. If the catalyst is contacted separately with olen and oxidizing gas as it has been set forth above, free halogen, especially chlorine or chlorine-containing hydrogen chloride, may be allowed to act on the catalyst together with the oxidizing medium, after or prior to the action of the oxidizing medium. It is also possible to allow halogen and olefin to act simultaneously on the catalyst, but in this case side reactions are liable to occur to a certain extent, such as a chlorination. Instead of using halogens or hydrogen halide for regulating the copper to halogen ratio, there may also be employed compounds yielding halogen ions under the reaction conditions, such as halogen-oxygen compounds or organic substances, e.g. saturated aliphatic halogen compounds of low molecular weight, such as ethyl chloride. If the catalyst contains more halogen than corresponds to the copper to halogen ratio of 1:2the reaction is retarded. In this case, part of the halogen ions may be removed, e.g. in the liquid phase by partial neutralization, precipitation or by meansl of anion exchangers. Alternatively, i-t is possible to wait until the Volatile halogen-containing -by-products formed have entrained so much halogen that the optimum ratio reappears.

The amount of halogen compound, necessary to adjust the proposed optimum ratio can be readilyk calculated andv controlled by periodic analyses. In .the simplest case the term halogen compound is here intended to mean hydrochloric acid. The copper analysis need only be made occasionally in view of the fact that the content of copper in the solution or in the solid catalyst practically cannot change. It is therefore suflicient to make periodic chlorine analysis, preferably by the usual rapid method.

In order to immediately adjust the optimum copper to halogen ratio in a fresh catalyst, part of the necessary cupric chloride may be replaced by cuprous chloride or copper acetate; this enables high conversions to be obtained from the very beginning of the reaction.

A constant copper to halogen ratio may be adjusted by adding the components continuously or discontinuously. According to a preferred variant, for example, aqueous hydrochloric acid is pumped into the contact solution by means of a regulable pump; alternatively, if smaller amounts of catalysts are concerned, some drops of hydrochloric acid are added to the catalyst in certain intervals of time.

If mainly aldehydes and ketones are to be prepared and the reaction is carried out in the liquid phase it is advantageous to additionally prevent or remove an accumulation of carboxylic acids, for example acetic acid, in the rea tion space. It is to be noted, that the halogen content in the liquid catalysts used in the present reaction may become depleted in the course of time. The loss of halogen may be counteracted by addition of halogen or hydrohalic acid or organic substances splitting oir` halogen or hydrohalic acid under the reaction conditions as already stated.

Such depletion of halogen is to be attributed substantially to the formation of volatile halogenated by-products, for example methyl chloride or ethyl chloride, which together with the carbonyl compounds produced entrain the halogen from the catalyst more or less rapidly. It has been ascertained that a certain amount of carboxylic acid corresponding to the olefin, is produced during the reaction, for example acetic acid; such acid concentrates in the liquid and increases the solubility of the reaction products. This favors the formation of halogen-containing volatile by-products and promotes the depletion of halogen. In addition thereto, the carboxylic acids which have concentrated, especially acetic acid, react with the copper ions which is unfavorable because the copper salts formed, such as copper acetate, are relatively inert towards the olefin oxidation. In many cases it is therefore necessary to counteract such accumulation of carboxylic acids in the react-ion space and to take care that these acids appear in as low a. concentration as possible. This may be done by suitable continuous or discontinuous measures, for example by distillation, extraction or precipitation. A preferred variant in operating under atmospheric pressure consists for example in that the carboxylic acids formed are allowed to distil over together with the evaporating water; the water consumed is then replaced b-y a corresponding amount of fresh water. The amount of carboxylic acid removed in this manner is dependent on the surface of the reactor, the temperature used and the amount of gas flowing through, and may be modified by varying these factors. According to another variant the entire contact solution is Worked up, carboxylic acid con tained in the catalyst is removed, and the contact solution is recirculated into the apparatus.

In order to avoid operative disturbances part of the contact liquid may be withdrawn periodically or continuously and freed from carboxylic acid, partially or substantially, for example by distillation, and the liquid obtained may be added again to the contact medium.

The conversion and the space/time/yield depend, for example, on the residence time in the apparatus and the composition ofthe catalyst, the temperature and the pressure used and, if liquid catalysts are used, furthermore on the line distribution of the gas. The optimum time of stay can readily be determined by those skilled in the art.

In the process of this invention care should be taken that the heat evolved during the process (high heat effect: about 60 kcal. per mol of aldehyde) is dissipated to the exterior.

if liquid catalysts are used, the present reaction may be carried out, for example, in vertically arranged reactors, such as tubes provided with frits or oscillatory agitators, or in' other usual reaction towers, for example wash towers, suitably filled with iilling material. The gases may be atomized, for example through a frit, or in another suitable manner, and too voluminous ygas bubbles may be divided into smaller ones, for example by means of an agitator. For this purpose there may also be used a vibro-mixer or a turbo-mixer. All these variants enable the reaction to be carried out continuously.

When using solid catalysts, the gases may be passed through a tube which is filled with the catalyst, or a fluidlzed bed catalyst may be applied.

Condensates which separate from the reacted gas, especially aqueous condensates, may also :be recirculated lf solid catalysts are used, they are of course vaporized to again participate in the reaction, for example as such or after separation of higher and/ or lower boiling reaction products.

it is not necessary that the catalysts used are lmade of fine chemicals; they may likewise be produced from suitable metals of commercial purity. Metals such as copper and iron may be readily dissolved even by non-oxidizing acids, such as hydrochloric acid and acetic acid. if desired by addition of an oxidizing agent, especially if copper is used, or by passing through during the dissolving process a gaseous oxidizing medium such as oxygen or air enriched with oxygen. The contaminations contained in commercially pure metals do not aiifect the reaction if the solutions obtained are used as catalysts or are worked up to solid bed catalysts for the olefin oxidation. More especially, the catalytic activity remains practically unaffected by small amounts of foreign metals which may appear in copper or iron of commercial purity. rEhe anion forming agents contained in metals, such as sulfur, phosphorus, car-bon, silicium etc. are converted upon being dissolved to either hydrogen compounds, for example H28, which escape together with the reaction gases, or oxidized to acids of a higher valence stage, for example H2804, which do not aect the reaction, or converted partially into insoluble compounds, for example CuS, which appear 1.4 only in minor amounts and, if necessary, can readily be separated from the catalyst, for example by filtration before the catalyst is used or the catalyst solution is applied to a carrier.

IThe solutions so obtained are then admixed with the noble metal compound which is added in substance or in the dissolved state, if desired diluted with water, and the concentration of hydrogen ions is adiusted to the degree desired; the solutions so prepared then directly be used as a catalyst for the olefin oxidation in the liquid phase, or they may be concentrated and be applied to a carrier, for instance to those mentioned above.

Solvents suitable for dissolving the `metals are chiefly hydrochloric acid and acetic acid in view of the fact that the presence of these acids proves especially advantageous in oxidizing oleins to aldehydes, ketones and acids. Acids other than those indicated above may, however, also be used, for example nitric acid. ln this case, it is preferred to remove the acid in excess in order to adjust the solu-v tion to the pH desired and to use the solution so treated as a catalyst or =for impregnating the carrier. if desired the salt of the metals may also partially be converted into the corresponding chlorides and/ or acetates.

Palladium chloride or other noble metal chlorides need not be used, since there may also be employed the metals themselves, e.g. metallic palladium, suitably in a nely divided and finely distributed state, which reacts, for example, with copper chloride, and is converted to palladium chloride or a compound other than palladium chloride.

For example, the catalyst may contain as anion chlorine ions or halogen ions other than chlorine, such as liuorine or bromine ions, nitrates or chlorateor perchlorate radicals yor mixtures of these anions, for example, with sulfate or acetate radicals. Sometimes it is especially advantageous to use a catalyst which contains perchlorate ions.

Although the catalysts have generally a good activity even after a prolonged time of reaction, especially when anions are added during the reaction, it may be advantageous to regenerate the catalyst from time to time. Some Variants for such regeneration methods are described hereinafter.

It may be that the activity of the catalyst, especially when the catalyst is used for a very long period of time, is more or less reduced by the Iformation of a minor amount of lay-products, or by foreign substances which may have been introduced. The byproducts formed consist partially of organic compounds which are water-soluble at least to a certain degree, such as acetic acid, o-xalic acid, higher aldehydes or ketones, or chlorinated organic compounds. These 1byproducts may entrain precipitations, for example of heavy metal oxalates. Foreign substances possibly introduced into the catalyst may derive from, for example, contaminations of the gases, or the corrosion of parts of the apparatus, for example iron parts or of the lining of the reactor.

The catalysts may be freed from these contaminations and regenerated in a simple manner by precipitating the noble metal compound as elementary metal and-if present--the cupric chloride as cuprous chloride. lf solid catalysts are used the precipitation may be effected directly on the carrier, or the catalytic compounds may be dissolved therefrom. Precipitation is preferably carried out with the exclusion of substantial amounts of oxygen by the action of carbon monoxide, hydrogen, or one or more oleiins, for example ethylene, propylene, or the butylenes, or of any other olefin or a mixture of several of these precipitating agents. The mixture of cuprous chloride and noble metal or the solid catalyst, in which those substances are precipitated, are advantageously washed, for instance with water. If a solution of the catalytic agents has been prepared or a liquid catalyst is used, it is mixed with water and an acid, suitably hydrogen chloride, 'if desired in the form of hydrochloric acid, and may then be reused in this state in the reaction or in the impregnation, or more suitably after oxidation with oxygen or an oxygen-containing gas, such as air. lf carboxylic acids are additionally to be prepared, a salt of iron, manganese and/or cobalt must be added before the impregnation. If the cuprous chloride and the noble metal are precipitated in the carrier, the washed carrier is treated with a solution of a salt of iron, manganese and/or cobalt and with an acid, such as hydrochloric acid and, if desired, is additionally oxidized, e.g. .by means of oxygen or chloride, and then reused. lf a particular oxidation is dispensed with, -an olefin and oxirdation agent are allowed to act simultaneously upon the catalyst to be reused, oxidation is brought about in the .following reaction by the oxidizing agent, especially by the oxygen contained in the reaction gas. After the re- `generated but not yet oxidized catalyst has been reintroduced into the reactor, the amount of oxygen contained m the `reaction gas may temporarily be increased, if desired. lf in reducing the catalyst oxygen is not corn- Jjletely excluded, it is only necessary to use a somewhat larger amount of reducing agent.

This mode of execution is especially interesting if in addition to the noble metal the catalyst contains substantial amounts of copper salts, since these two rather expensive components of the catalyst-CuCl and noble metal-precipitate, while all other impurities or additions, for example iron salts, remain in the solution and are thus separated from the expensive noble metal and copper compound.

The noble metal is quantitatively precipitated as well as CuCl, except for a minor amount thereof which is soluble in water. In reusing the catalyst it is therefore Iadvisable to add the corresponding amount of fresh CuCl2 and/or CuCl--i-HCl. If the catalyst contains further additions, such as iron salts, it is also suitable to replenish these frequently cheap substances.

The simplest manner of allowing CO and/or olefins and/or hydrogen to act upon the catalyst is to allow these substances to act upon the solid catalyst or to introduce them into the catalyst solution. In most cases this may tbe done under normal conditions, but it may be advantageous to use a higher temperature and/or a raised pressure. More severe conditions are opportune especially when hydrogen is used, which is the weakest reducing agent among the substances mentioned above. In using oleins as reducing agents the oxidizing activity of the catalyst may be used for a further formation of aldehydes, ketones and acids.

It is furthermore advisable prior to allowing the above gases to act upon the liquid catalyst or upon the solution which is obtained by dissolving the active components from the carrier, to entirely or partially neutralize or :buffer the acid to a relatively low pH which is preferably in the range between 2 and 4. At too strong an acidity the reaction proceeds too slowly or is incompiete after the usual time of reduction. In addition thereto CuCl is remarkably soluble in concentrated hydrochloric acid, which may involve losses of copper. It Should be noted that a further amount of hydrochloric acid is formed during the reduction of the copper or noble metal chloride, and this amount of acid must possibly also be neutralized or buffered. Reduction at a pH higher than 4 is often regarded to be disadvantageous since hydroxides are likewise precipitated, though a regeneration by precipitating the hydroxides or basic Salts of the metals used is likewise possible.

Neutralization or buffering may be made in the usual manner with alkaline reacting substances, such as sodium hydroxide solution, sodium carbonate, sodium acetate, chalk, lime and similar compounds. The said reducing gases may be circulated for reasons of economy and, especially if carbon monoxide. is used, may also be subjected to a CO2 wash. If a larger amount of catalyst is used, it is advantageous in order to avoid operating .distttirbines IO Tegel'lfle al 'ays a small amount of cat- 16 alyst and subsequently to add the regenerated portion to the major quantity of said catalystl A possibility to recover palladium metal from liquid catalysts consists in subjecting the catalyst in known manner and in a strong acid medium to the action of acetylene. A palladium-acetylene compound precipitates which can be readily separated and freed from cations and anions by means of a Water wash. The palladiumacetylene compound so obtained may be then converted in the air or in the presence of ammonium nitrate to palladium oxide which in turn is capable of being converted directly to the chloride by means of hydrochloric acid. In this variant it is especially advantageous that acetylene can act on the palladium compound in the presence of hydrogen.

According to another method a solid bed catalyst may be regenerated by arresting the olefin supply for a short while and treating the catalyst' simultaneously with oxygen or oxygen-containing gases and steam and an acid in vapor form or gas form, preferably hydrogen chloride or hydrogen bromide. A variant of such regeneration consists, for example, in passing oxygen or an oxygen-containing gas partially or completely and prior to contacting the catalyst through aqueous hydrochloric acid, preferably at a raised temperature. Accurately dosing the hydrochloric acid is especially simple, if a 2O percent hydrochloric acid is used.

The catalyst which prior to this treatment has possibly a metallic lustre turns again brown and regains its initial activity, possibly after an induction period of several hours.

The apparatus used in the process of this invention should be made of a material which is not corroded by the catalyst and preferably, especially if solid catalysts are used, has a sucient thermal conductivity. Since the catalysts used contain noble metal compounds, for example palladium compounds, it is less suitable to use the usual metals and alloys as construction material, since there is the risk that these less noble metals, in the presence lof Water and at the indicated temperatures, precipitate the noble metal salt used in the catalyst, and that they themselves are converted into salt form.

In order to avoid corrosion in the apparatus used, it is often suitable to use an apparatus lined with titanium or titanium alloys containing at least 30 percent of titanium, or with tantalum. There may also be used `glass vessels or enamelled or rubber-lined vessels. The reaction may also be carried out in brick-lined vessels or, under suitable reaction conditions, in vessels the insides of which are lined with plastic material, for example polyolens, polytetrafluorethylene or hardenable unsaturated polyesters or phenol, cresolor xylenol-formaldehyde resins. As brick lining there may be used, for example, ceramic material, carbon bricks impregnated with hardenable articial resins and similar known materials.

The following examples illustrate the invention but they are not intended to limit it thereto.

Example 1 0.5 gram of PdCIz, 50 grams of CuCL2H2O and 5 grams of the potassium salt of 1.2-naphthoquinone-4- sulfonic acid are dissolved in 500 grams of water. The catalyst solution so prepared in introduced into a vertically arranged tube and 8 liters of ethylene and 4 liters of oxygen are passed through per hour at 75 C. The con tent of acetic acid in the catalyst is kept small be continuous removal of acetic acid by distillation. The Water which distills over is replaced by fresh water. The molar ratio of copper to chlorine is kept between 1:1.4 and 1:1.8 by continuous addition of small amounts of hydrochloric acid. About 50% of the ethylene used are converted to acetaldehyde. The residual gas is reused in the reaction after the acetaldehyde has been removed by washing.

l 7 Example 2 0.5 gram of PdCl2, 50 grams of CuCl2.2I-I2O and 5 grams of the sodium salt of anthraquinone-Z-sulfonic acid are dissolved in 500 grams of water. The procedure is otherwise the same as described in Example 1. More than 30% of the ethylene are converted in acetaldehyde.

We claim:

1. A process for the conversion of an olenic hydrocarbon to a carbonyl compound selected from the group consisting of aldehydes and ketones by oxidation of an olelinic carbon atom of said olenic hydrocarbon to a carbonyl group, which process consists essentially of contasting said olenic hydrocarbon and oxygen, in a neutral to acid medium, with water and a catalyst of (a) a salt of a noble metal selected from the group consisting of palladium, iridium, ruthenium, rhodium, and platinum, and (b) as a redox system, an inorganic salt of a metal showing several valence states under the reaction conditions applied, said contacting taking place in the presence of a quinone selected from the group consisting of unsubstituted quinones, quinone carboxylic acids, and quinone sulfonic acids.

2. A process as in claim 1 wherein the reaction is carred out at a temperature of from 40 to 180 C. at a piessure of from atmospheric pressure to 50 atmospheres gauge pressure, said medium has a pH of from 0.5 to 3, and said quinone is present in an amount of from 0.1 to 10 percent by weight of said catalyst.

3. A process as in claim 1 wherein said noble metal is palladium, said metal showing several valence states is copper, and said quinone is a quinone sulfonic acid.

4. A process as in claim l wherein halide ions are supplied to said catalyst during the course of the reaction.

5. A process as in claim 1 wherein said olem'c hydrocarbon has 2-4 carbon atoms.

6. A process for the conversion of an olenic hydrocarbon having 2-4 carbon atoms to a carbonyl compound selected from the group consisting of aldehydes and ketones by'oxidaton of an olenic carbon atom of said olenic hydrocarbon to a carbonyl group, which process consists essentially of contacting said olenic hydrocarbon and oxygen, in a medium having a pH of from 0.5 to 3, at a temperature of from 40 to 180 C. and at a pressure of from atmospheric pressure to atmospheres gauge pressure, with water and a catalyst of (a) palladium chloride, and (b) as a redox system, copper chloride, said contacting taking place in the presence of from 0.1 to 10 percent, by weight of said catalyst, of a quinone sulfonic acid.

References Cited in the tile of this patent UNITED STATES PATENTS 1,999,620 Van Peski et al Apr. 30, 1935 2,055,269 Van Peski et al Sept. 22, 1936 2,333,216 Trieschmann et al Nov. 2, 1943 2,451,485 Hearne et al Oct. 19, 1948 2,486,842 Hearne et al Nov. l, 1949 2,690,457 Hackmann Sept. 28, 1954 FOREIGN PATENTS 664,879 Germany Apr. 1, 1930 575,571 Great Britain Feb. 25, 1946 

1. A PROCESS FOR THE CONVERSION OF AN OLEFINIC HYDROCARBON TO A CARBONYL COMPOUND SELECTED FROM THE GROUP CONSISTING OF ALDEHYDES AND KETONES BY OXIDATION OF AN OLEFINIC CARBON ATOM OF SAID OLEFINIC HYDROCARBON TO A CARBONYL GROUP, WHICH PROCESS CONSISTS ESSENTIALLY OF CONTACTING SAID OLEFINIC HYDROCARBON AND OXYGEN, IN A NEUTRAL TO ACID MEDIUM, WITH WATER AND A CATALYST OF (A) A SALT OF A NOBLE METAL SELECTED FROM THE GROUP CONSISTING OF PALLADIUM, IRIDIUM, RUTHENIUM, RHODIUM, AND PHATINUM, AND (B) AS A REDOX SYSTEM, AN INORGANIC SALT OF A METAL SHOWING SEVERAL VALENCE STATES UNDER THE REACTION CONDITIONS APPLIED, SAID CONTACTING TAKING PLACE IN THE PRESENCE OF A QUINONE SELECTED FROM THE GROUP CONSISTING OF UNSUBSTITUTED QUINONES, QUINONE CARBOXYLIC ACIDS, AND QUINONE SULFONIC ACIDS. 